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FAQs on Carbon Filtration, Renewal/Life

Related FAQs: Carbon 1, Carbon 2, & FAQs on Carbon: Rationale/Use, Types/Qualities/Selection, Placement, Negative Reactions, Sources/Brands, & Marine Chemical Filtrants

Related Articles: Selection and Placement of Activated Carbon in Marine Aquaria by Adam Jenkins,  Phosphates in Carbon; An analysis of the phosphate content of activated Carbon by Steven Pro, Marine Chemical Filtrants,

Depending on initial quality, quantity... the bio-load, other water chemistry... carbon is "exhausted" minutes to hours after application... still useful biologically however. Not worthwhile for home hobbyists to try to recharge. RMF

Chemi Pure still usable?    10/24/12
I put new Chemi Pure in my tank, ran it for several weeks. Then, I pulled it out and let it sit in a bucket of saltwater for 2 months (i.e., while treating my main display tank). As one would expect, the bucket does not smell very good at the moment...
Do you think there is any problem with placing it back in service?
<Might be "used up" (saturated) but should be okay (at least as bio-media) with a good freshwater rinse/soak. BobF>
Thanks, Dave 

"Reactivating" Activated filter carbon    6/23/12
Hi crew,
I just wanted to follow-up on a question I posed a while back.  I think I a partial answer that I'd like to share with you.  If you think it would be of value to your readers, feel free to post/share. 
<Thank you>
My original question asked if it were possible to regenerate activated carbon.  Yes, I'm cheap.  But more than that, I'm practical and like the sustainability aspect of this idea.  While I could rinse and throw my old carbon in the garden, I'd simply like to re-use it.  My initial thought was to resubject it to >500oF temperatures for a period of time.  I don't claim to be a grille master, but I seem to be able to make my own "carbon" by over cooking the burgers.  So, I figured, if I just applied my skill to my old carbon..  you get the idea.   As I understand it, our carbon, while in use, is adsorbing into is microscopic pore molecules like dyestuffs, iodine and other large molecules.  A great test is to pour Kool-aid through a bed of this and see the drink come out of the carbon colorless (although just as tasty).  The dyestuff is retained.  Well, those dyestuffs, colors and other large molecules are all just complex organic molecules.  I'm sure with enough heat they can be reduced to CO2, carbon and a few other trace elements (P, N, S, etc.) just like my burgers.
<For the most part, yes>
So, I put it to a test.  I put 4 cups of my spent carbon that was in use for a couple of months (nasty smelling too) into a Corning bake ware dish and set it into a 525oF grille for about 45 minutes.  After allowing it to cool down (and cleaning the inside of my dish back to white), I reused the carbon.  Note:  the carbon was odorless after coming off the grille and cooling down.  The carbon was used in my DIY carbon pre-filter on my RO/DI unit.  AND there were no detectible levels of Chloramine/Chlorine exiting the carbon chamber.  The feed water contains >6 PPM chloramine.   In my aquarium, the water had a slight yellow tint.  After 36 hours of filtering with a Magnum canister filter using only 2 cups of this carbon, the 170 gallons of aquarium water was near colorless to the eye.
I don't know to what degree carbon can be regenerated.   I presume of the dyestuff turns to ash inside the pores at >500oF.  Repeating this process may eventually clog the pores.  I presume the carbon may slowly loose activity with this kind of regeneration, but it does seem to work.  I supposed for carbon used to remove potable water chloramine (pre-RO treatment), the Chloramine will oxidize to Cl2 and NOx and subsequently off-gas.
I thought I would share my knowledge and invite anyone else with ideas on the subject to build on this.
Happy reefing,
Steve Ghera
<Thank you again for this report. Bob Fenner>

Phosban Reactor and Carbon Reactor (Runtime) – 02/23/12
Hello Crew,
<<Hey Ed>>
Just a quick question. How often should my Phosban 150 reactor and separate carbon reactor be running? Should they both be running 24/7? Both of my reactors are hanging in my 30 gallon sump.
<<Some might say to run these on a punctuated basis…but I see/have seen no harm in running 24/7, and do this with my own system.  But saying that, do keep an eye on your system/livestock and see what it/they have to tell you about it>>
<<Happy to share…  EricR>>

Regenerating Filter Carbon -- 12/20/10
Dear Crew,
I would like your insight on regenerating filter carbon. I saw one post in the WWM FAQ on this from a person in Texas. I have some highly activated filter carbon that I think may be spent by virtue of the water
beginning to show yellowing again. This stuff runs about $25 per half gallon of carbon.
<Carbon has a useful life of about two weeks. Generally, it needs to be replaced after that with new carbon. With this said, there are almost no situations where carbon is useful in freshwater fishkeeping outside hospital tanks and other situations where removing old medicines is important. Carbon is a legacy of the past, when people avoided water changes, i.e., did about 10-20% water change per month. The theory was that "old" water was better for fish. Anyway, old water tended to become yellow with tannins, and the carbon removed those tannins. This was a purely cosmetic fix, and in practical terms did very little to improve water quality as the fish experience it. Carbon didn't remove, for example, nitrate. So once it was realised old water was actually bad for fish, in particular because of high nitrate levels, they switched to frequent water changes, 25% per week or more. This in turn flushed out the dissolved organic chemicals that turn water yellow, so between weekly water changes the water shouldn't become noticeably yellow. Hence carbon stopped being used by advanced and experienced aquarists, and is no longer recommended in modern aquarium books as a default addition to an aquarium. Retailers still
sell carbon, partly because marine aquarists do have uses for it -- water changes are more expensive in marine aquaria, and the fish more sensitive to dissolved organic chemicals that might lower pH, so carbon does something useful. But mostly carbon continues to be sold because it's a high profit, low cost item.>
I routinely use my self-cleaning oven at home to clean a ceramic pizza stone and the stainless steel cooking grates from my BBQ grille. Doing this chars virtually every thing organic out/off these items. The porous
ceramic stone nearly looks new. The black cheese and sauce stain almost disappear. So this makes me think that putting porous carbon in the oven with these other items would do the same for this carbon. That is, all the organic matter would turn to carbon black. Molecules like organo-phosphates would of course be reduced to elemental Phosphorous or POx; amino acids to carbon and NOx; sulfur compounds to SOx. I imagine over time the accumulation of these ashes will reduce the pore size in the carbon thus rendering it "not so active".
<Yes; in fact this is a dramatically important aspect. Activated carbon isn't merely carbonised wood or whatever, it's charcoal that's been "sintered" so that it has a massive surface area relative to the size of
each grain.>
I'm writing just to inquire about any concerns you see in running an experiment like this. I'd put "spent carbon" on the pizza stone the next time I do an oven, stone, grille rack cleaning for about 4 hours at a
temperature of >550 degrees F. Then I would use that carbon to see if the yellow vanishes from the aquarium water like it did when the carbon was new.
<Insofar as carbon does nothing even remotely useful in the modern freshwater aquarium, feel free to experiment away. Old carbon is a good medium for biological filter bacteria, and after a couple of weeks operates more as biological media than chemical media. 287 C/550 F isn't nearly hot enough to create fresh carbon, and unless your oven is filled with nitrogen gas rather than air, you can't replicate the 500+ C temperatures and inert gases required to create new carbon.>
Thanks for your thoughts, - - Steve G.
<Cheers, Neale.>
Re: Regenerating Filter Carbon -- 12/20/10
Dear Neale,
Thank you so much for the reply.
<Most welcome.>
I failed to mention my application is a "garden" reef. I know: tisk, Tisk.
<Ah, well, do read here:
After reading much more on WetWebMedia on how to plan for reef stocking, I will be slowly shifting towards a more natural mix of corals. Currently I have LPS (torch & frogspawn) SPS (various Acroporas), soft corals (xenias, mushrooms, and Sarcophytons), rose bubble tip anemone and a maxima clam.
The display tank is a 135 gallon plumbed to two 30 gallon frag tanks. The softies and the rose BTAs multiply quit a bit ( went from 1 to about 20 in 3 years; and I can't remember how many I have given away on top of that - they are like tribbles from Star Trek).
My application of carbon was to reduce yellow water and abate chemical warfare between coral species. While skimming and water changes seem to keep things "in balance", the LPS polyps don't extend like they did when they were the only corals in the tank and the tank was new. Using fresh carbon seems to correlate with created frogspawn polyp extension.
<Quite possibly so.>
I think I will experiment with oven baking the carbon and report what I find. Another idea I have is to get some time in a pottery kiln at a local art shop. It gets over 1000 degrees F but is not inert.
<Hard to imagine that this will either work or be cost effective, but by all means try!>
Thanks again,
<Cheers, Neale.>

Reactivate Activated Carbon? -- 11/24/07 Hello crew, John here. <<Hey John, Eric here>> I have a question. <<Okay>> Is there any way I can reactivate activated carbon, so I don't have to keep buying it all the time? <<I've wondered that myself before'¦and from what I recall the process (extremely high temperatures/pressures), as well as the expense involved, render this impractical'¦at least for hobbyists>> Thanks for your time, John. Happy Holidays. <<Happy to help. EricR>>

Recharging Chemi-Pure? -- 11/25/07 Hello all, <<Morning Whit>> Thanks in advance for your help. <<A pleasure>> I was wondering if there is any way to recharge Chemi-Pure? <<Not that I am aware>> I have looked and looked, but can't find any information. <<This product is a combination of carbon and an ion-exchange resin. It's not possible/practical/economical for the hobbyist to regenerate carbon (requires considerable investment in a multiple-hearth furnace capable of generating temperatures of 800 °C)'¦and while it 'is' possible to regenerate the ion-exchange resin (generally an overnight soak in a bleach solution), the effort required to separate the tiny resin beads from the carbon will likely prove to be non-worthwhile>> Also, what are your thoughts regarding original Chemi-Pure, and the new Chemi-Pure Elite. <<I think the original Chemi-Pure is great stuff'¦the efficacy of the new 'Elite' version with the added iron-based phosphate remover remains to be seen>> Is the Elite worth the cost difference? <<At almost twice the price with a 17% increase in volume (10oz vs. 11.74oz) I'm inclined to stick with the original, and purchase an iron-based phosphate remover separately to be run/maintained in a separate reactor>> Thanks! Whit <<Glad to assist. EricR>>

Thermal Reactivation of Carbon Hello all, I have a quick question as to the re-use of carbon in my reef tank. <Yes, surely> The use of granular activated* carbon (GAC) tends to be the best available method for removing dissolved organics and some inorganic chemicals from our reef tanks by adsorption. It is assumed that the inorganic chemicals are removed through a properly functioning RO/DI process and are not re-introduced into the reef system at another stage. Organics are introduced by various biological processes which are occurring in the reef system. When those organics have saturated the available GAC and it has reached its breakpoint, shouldn't it be possible to regenerate the GAC with the application of heat to burn up the organic molecules which have been captured? <In a lab environment, certainly> In water treatment applications it is mentioned that GAC can be reactivated but at an interval of 1 to 2 years. Any thoughts on this matter? <I have heard many thought on the re-activation of carbon, both in home and in laboratory environments.  I'm not certain why I haven't heard about home success regarding this.  In the business world, I believe something called a "Carbon Reactivation Kiln" is used, but they're typically a custom made item.  This leads me to assume that the resources for obtaining new carbon are less costly than re-activating saturated carbon.  I would encourage you to keep the flow of information coming- Much research on matters like this is unavailable to the daily aquarist because it's private research.  It's in my nature to encourage recycling and reusing extinguishable resources.  Thanks for contributing, Ryan Bowen> Thanks for any information you can supply. <It's not much, but perhaps this is a good starting point: http://webstore.ansi.org/ansidocstore/product.asp?sku=ASTM+D6781-02> David McFadden Dallas, Texas * The term activated refers to the high-temperature removal of tarry substances from the interior of the carbon granule, leaving a highly porous structure.

Carbon use 3/11/05 Just a quick question about carbon use. I'm planning to use one of the WWM FAQs recommended brand in small amount on a continuous basis changing it maybe each two weeks. <changing small amounts (weekly) frequently is always better than larger monthly> I understand it is better to have the water forced through it instead of dropping the bag in the sump. <correct... unless it is only used for color/odor control> However, I don't want to kill/trap plankton by forcing the whole flow of water through it. <a small concern> Same for the use of a hang on power filter with carbon. <easily avoided by putting a foam block on the intake... extend the life of chemical media too!> Maybe block part of the water flow with the bag of carbon, but water following the easiest path I don't know if it's much different than dropping the bag in the sump. <over thought... no worries> And then again, some plankton are going to be pushed and trap on/in the bag. What's the best plankton-friendly option for me? Thanks!!! Dominique <best regards, Anthony> - Carbon Use, Follow-up Bob, <JasonC here in his stead.> I took your advice and bought the canister filter (Hot magnum) I will probably use it once a month and let it run for a few days with carbon. Do you think I should dispose of the carbon after using it for a couple of days or would it still be good to use a few more times?  <Nope... the carbon is pretty much spent after 24 hours. Does all the good it's going to do in those first couple of days. Do not re-use.> Thanks again for your help! <Cheers, J -- > 

Carbon in a marine tank  9/23/05 A quick question: I've read through the Conscientious Marine Aquarist and your website. In the book it says that activated carbon has an effective life of two to three months. But in a few of the answers to daily questions recently it was stated that in a marine tank carbon only has an effective life of 24 hours. Is there a definitive answer? <The quality of the carbon has a lot to do with how much dissolved waste it can absorb.  The bio-load of the tank the carbon is being used on is another factor along with whether a protein skimmer is being used in conjunction with the carbon.  There is really no realistic time span that carbon is effective.  Case in point.  Chemi-Pure claims a six month life.  Two months max for me. Not saying it's not effective for six months, just not in my tank.  James (Salty Dog)> Thanks for you help! Berlin style set-up/carbon Bob- As a follow up question regarding mechanical filtration: I have a Magnum with a canister filter. My plan was to use it two - three days a month with carbon. When I remove the carbon should I replace the canister with the regular filter and run it all the time? I always thought that this would be an ideal place for waste build-up resulting in higher phosphates, etc... Also, what type of carbon do you recommend? Thanks again, Rob <Ah, good to hear... If it were me, I'd just leave the Magnum running continuously, replacing the carbon once a month (though it will be exhausted in a few hours...). I would place the carbon in a Dacron/polyester bag (many units already come in one), behind a layer or disposable filter fiber, and before two grades of permanent (but washable) Eheim Fein and Grob flocken (great plastic media that lasts... forever)... Bob Fenner>

Carbon Dear Bob, There are a lot of opinions on the use of carbon in a reef tank. Some say use it all the time, others say every other month, some say not at all. Even the amount to use is a mystery. What is your opinion? I'd like to know if I should use it all the time, how much to use, and which brand is gives the most "bang for the buck". Thanks again, Tony > Thanks for asking... IMO, most people, for most types of set-ups would/will receive sufficient "bang for the buck" advantage in using activated carbon about once a month... the amount is of course going to vary depending on the livestock, feeding, other filtration, quality of carbon... and much more... but something in the way of about a ounce per ten gallons of real system water (minus decor) is about right... On our old service company accounts we used to have two units of Chemipure (one older, up to two months, the other the newer, less than one month old) replacing the oldest one every month. My favorite brand, bar none is the HR (High Retention) Carbon sold by Tropical Marine Centre out of the UK (distributed in the US by other folks). This superb product holds onto undesirable materials but doesn't interfere with alkalinity or biominerals... an important claim. Place such "free" activated carbon in a reusable Dacron/polyester bag. Bob Fenner, who could go on

Activated Carbon I'm confused about the use of activated carbon in my marine aquarium. The advice I have read/heard ranges from activated carbon is only good for a couple of days and then should be thrown out to keeping activated carbon up to two months. I have a hang on power filter and would like to know what is the proper use of activated carbon under normal operating conditions, as well as it's other applicable uses. > You can read my take on activated carbons and other chemical filtrants posted in articles, et al. on the site: www.wetwebmedia.com For the short version: Activated carbon is a useful material to use, generally periodically to remove excess organics... Most forms have the shortcoming of removing too much in the way of biominerals and other useful materials as well. Even the best activated carbons only "last" minutes to hours in actual application. So "over-using" them is of small concern... unless you're switching out your AC every day...  Most folks who do use carbon, as I say, do so on a periodic basis... I suggest once a month... And yes, there are "rules of thumb" about how much AC can/should be applied in a filter flow path... The best "assays" are you and your livestock. For you, looking at a piece of white paper, end to end through the long path of your fish tank, before and after the carbon will surprise you... the water will be much less "yellow"... For your livestock, closely observing their reaction to water quality will tell you about how much carbon you ought to use, how frequently. One stipulation here... be careful to not "overuse" carbon... in terms of improving water quality in the way of strikingly improving light transmission... the first time out, it isn't too hard to actually photo-shock (burn) your photosynthetic livestock. Bob Fenner

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